Vacuum variable condenser



April 9 J. E. JENNINGS 2,883,593

VACUUM VARIABLE CONDENSER Filed March 12, 1954 /N VE N 70/? JO EMMETT JENNl/VGS falf mg fill! ATTORNEY United States Patent 2,883,593 VACUUM VARIABLE CONDENSER Jo Emmett Jennings, San Jose, Calif assignor to Jennings Radio Manufacturing Corporation, San Jose, Calif., a corporation of California Application March 12, 1954, Serial No. 415,873 4 Claims. (Cl. 317-245) My invention relates to electrical condensers or capacitors; and one of the objects of the invention is to provide a variable condenser enclosed within a vacuumized envelope, and in which moving mechanical means for varying the capacity of the condenser is also entirely within the vacuumized envelope.

Another object of my invention is the provision of a vacuum variable condenser in which variation is etfected by a rotor within the vacuumized envelope and responsive to an electromagnetic field produced by means exterior to the envelope.

Another object of my invention is the provision of a vacuum variable condenser in which the volumetric capacity of the vacuumized envelope and the degree of vacuum remains constant throughout its range of variation in capacity.

Another object of the invention is the provision of a vacuum variable condenser embodying means by which the setting of the condenser plates may be accomplished at a distance from the condenser.

Still another object is the provision of a vacuum variable condenser which employs no electric wires, coils or separate contacts of any kind within the envelope.

An additional object of my invention is the provision of a variable condenser in which vibration of the plates is prevented and exact alignment of the plates is maintained, so that extremely close spacing of the plates is possible without danger of shorting.

Speaking generally, the object of my invention is the provision of a compact vacuum variable condenser of rugged construction, having wide service application, and requiring substantially no maintenance during service.

My invention possesses other objects, some of which with the foregoing will be brought out in the following description. I do not limit myself to the showing made by the said description and the drawings, since I may adopt variant forms of the invention within the scope of the appended claims.

Broadly considered, my condenser comprises a series of closely spaced, substantially parallel, fixed copper plates and a mobile or movable series of similar plates, both sealed within a vacuumized envelope. The plates of the mobile series are interleaved with those of the fixed series. Each series of plates is electrically connected to a separate terminal or lead extending to the outside of the envelope. One of these leads is connected to ground.

A rotor is journaled inside the envelope adjacent the mobile plates, and is linked thereto by means which cause rotary motion of the rotor to impart a linear motion to the mobile plates toward or from the fixed plates. These means may include threaded elements on both rotor and mobile plates. A stator with appropriate connections to a source of electrical energy is mounted outside the sealed envelope and energizes the rotor which lies in its electromagnetic field when current flows to the stator.

The figure of the drawing is a half-sectional view of my vacuum variable condenser, the plane of section being in the longitudinal axis of the condenser.

My condenser comprises a pair of flanged end caps 2 and 3, preferably of copper, which constitute exterior terminals or leads, and also lugs by which the condenser is supported in suitable brackets. In each of these caps, component parts of the condenser are assembled before they are joined together to form a complete envelope by the glass shells 4 and 5 and the copper junction ring 7.

The glass shells or envelope sections are connected to the flanges 6 of the caps and to the junction ring to form vacuum tight seals 8. At each end, the glass is shaped into a reentrant portion which forms hollow annular extensions 9 and 10 on the main body of the condenser. The extension 10 is made with the walls quite close together, since it will contain a part of the operating mechanism and it is desirable to keep the overall thickness of the annular extension as small as practicable.

End cap 2 provides a rigid mounting for the fixed plate assembly 11, which is made up of a series of concentric cylindrical shells integrally united by brazing to each other and to a base plate 12 as shown. The fixed plate assembly 11, in turn, is integrally united to end cap 2 by brazing the inner end of the cap to the base plate and to the tabs 13 struck up from the base plate in a shape complementary to the end of the cap. This provides .a rigid structure concentrically arranged about the long axis 14 of the implement, and one in which the conduction of heat and current is at the maximum.

Mobile plate assembly 16 is similarly made up of a series of concentric cylindrical plates or shells fixed rigidly in the cone-shaped apertured mounting plate 18, all integrally united by brazing.

Means are provided for mounting the assembly of mobile plates 16 for movement back and forth and in interleaved relation with the fixed plates. Brazed into the end cap 3 is a plug 19 carrying the stud shaft 21 preferably of steel. Journaled on the stud shaft is a sleeve 22, one end 23 of which is brazed within the inner shell 24 of the mobile plate assembly; and the other end of which is threaded. The cone-shaped plate 18 is also brazed to the sleeve at a point 25 removed from the end 23; and thus rigidly braces the sleeve and mobile plate assembly upon the rigidly extending stud shaft. A stop washer 26 is held on the reduced end 27 of the shaft by a split ring 28.

The sleeve 22 is prevented from rotary movement while permitted axial movement by the resilient metal diaphragm 31, brazed to the junction ring 7 at its outer margin and to the sleeve closely adjacent the mounting shell 18. The diaphragm is provided with an aperture 32 adjacent its outer margin to avoid an isolated pocket within the vacuumized envelope. Although in minor degree, the effect of the diaphragm is to brace the central structure against lateral vibration. The diaphragm also serves as an excellent conductor of electricity and heat from the mobile plates to the junction ring.

Threaded on the threaded end of the sleeve is the nut constituting the hub 33 of the cup-shaped rotor 34, the cylindrical portion 35 of which extends into the narrow annular space between the walls of the annular extension 10. The rotor which is preferably of copper, is journaled in the radial and axial thrust bearing 36, fixed in the apertured cup 37, fixedly mounted on the end cap 3 between the plug 19 and the shaft 21, with the cup bottom edge brazed in the shallow annular groove 38 in the flaring flange 6 of the end cap. Rotation of the rotor thus slides the threaded sleeve 22 along the shaft 21, moving the plate assembly 16 into or out of the fixed plate assembly, according to the direction of rotation. The limit of movement is set by stop 26 and 3 the bottom of the cup 37, the diaphragm 31 offering no material resistance to the axial swing of its central part. Means outside the vacuumized envelope are provided for applying a rotating force in either direction to the rotor. Field coils 39 of a polyphase reversible motor are carried on a frame 40mounted on the external stud portion 41 of the end cap 3; and are energized through suitable wiring 42 and leads 43 extending to the point of control which may be quite remote from the condenser; and which will include conventional means for changing leads to reverse direction of rotation of the rotor.

The field coils are arranged as shown, on each side of the annular extension of the envelope and as close as possible to each other, since it is the magnetic flux between them that influences the rotor rim 35 and causes the rotor to revolve. While I have shown a polyphase A.C. reversible motor as the most economical one to use, other arrangements adapted for A.C. or DC. may be substituted.

Since the junction ring 7 is integrally connected by the diaphragm 31 to the sleeve 22 and movable plate assembly, a lead 44 from the ring connects the mobile plate assembly to ground as shown. The junction ring also bears a continuous circular flange 46, constituting an electrostatic shield between the two ends of the condenser.

The flange also greatly increases the radiation of heat flowing into the junction ring from the plates.

It is noted that in the condenser just explained there are no wires, coils or contacts within the envelope; and that the exciting coils of the stator are outside the envelope and easily reached for repairs or replacement in the event of need. The avoidance of vibration in the entire assembly is of extreme importance since the clearance between the fixed and movable plate assemblies is of the order of only .002" or .003".

Stiffness and rigidity in the mobile plate assembly mounting on a long and finely threaded sleeve and central stud shaft is assured by the heavy construction and the bracing effect of both the diaphragm 31 and the bearing cup 37. Low load lubrication of the rotor hub on the threaded sleeve 22; and of the latter on the stud shaft 21, may be secured by arranging steel against silver, as by silverplating the sleeve, and making the stud shaft and threaded center of the hub of steel. A high temperature lubricant comprising a compound of molybdenum is also satisfactory.

Since the interior of the envelope is vacuumized and the rigid wall uninterrupted by a bellows or otherwise the volumetric capacity of the envelope and the internal pressure on the movable plates remain constant, so that the torque required to move the plates also remains constant and adherence to accurate calibration is assured.

The assembly of the glass shells on the junction ring and the subsequent evacuation Oif the envelope are conventional and need not be detailed here.

I claim:

1. A vacuum variable condenser comprising a vacuumized envelope including two aligned and generally cylindrical glass shells, a metal ring forming a vacuum tight connection between adjacent edges of the shells, metal end caps closing remote ends of the connected shells, a condenser plate fixedly mounted inside the envelope on one of the end caps, a stud shaft fixedly mounted inside the envelope on the opposite end cap, a mobile condenser plate journaled on the stud shaft, a flexible metal diaphragm integrally connecting the mobile plate to the metallic ring, a rotor inside the envelope and mounted for rotation on said opposite end cap, means connecting the rotor to the mobile plate to move the latter toward or from the fixed plate on selective rotation of the rotor, and electrical means outside the envelope to ener gize the rotor.

2. A vacuum variable condenser comprising a vacuumized envelope including a generally cylindrical shell and conductive end caps closing opposite ends of the shell, one of the ends of the shell having a reentrant portion enclosing an annular extension of the chamber within the envelope, a stud shaft fixedly mounted inside the envelope on the end cap adjacent the reentrant portion of the shell, a condenser plate fixedly mounted inside the envelope on the other end cap, a mobile condenser plate mounted on the stud shaft, a rotor inside the envelope extending into the annular extension of said chamber and mounted for rotation on said adjacent end cap, means connecting the rotor to the mobile plate to move the latter relative to the fixed plate, and electrical means mounted on said adjacent end cap outside the envelope and on both sides of said reentrant portion thereof to energize the rotor.

33. Avacuum variable condenser comprising two aligned and generally cylindrical glass shells, a metal ring forming a vacuum tight connection between adjacent edges of the shells, each of the remote ends of the connected shells having a reentrant portion enclosing an annular exten sion of the chamber within the shells, metal end caps closing the opposite open ends of the connected shells to form a complete envelope, a stud shaft fixedly mounted inside the envelope on one of said end caps, a condenser plate fixedly mounted inside the envelope on the other end cap, a mobile condenser plate mounted on the stud shaft, a rotor inside the envelope extending into one of said annular extensions of the envelope chamber and journaled for rotation on the adjacent end cap, means connecting the rotor to the mobile plate to move the latter relative to the fixed plate, electrical means mounted on said adjacent end cap outside the envelope and on both sides of the adjacent reentrant portion thereof to energize the rotor, and a radially extending metal flange integral with and circumscribing the metal ring.

4. A vacuum condenser comprising a vacuumized envelope including a generally cylindrical shell and conductive end caps closing opposite ends of the shell, a condenser plate fixedly mounted inside the envelope on one of the end caps, a stud shaft fixedly mounted inside the envelope on the opposite end cap, a mobile condenser plate having journal means slidably'supporting said mobile plate on the stud shaft, electrical conductive means connected to the mobile plate and leading to the exterior of said shell, a rotor inside the envelope and mounted for rotation on said opposite end cap, a second journal means connected to said rotor and supported by said stud shaft, said second journal means being slidably movable along said stud shaft responsive to rotational movement of said rotor and said second journal means and said mobile plate being interconnected to move the latter toward or from the fixed plate on selective rotation of the rotor, and electrical means outside the envelope to energize the motor.

References Cited in the file of this patent UNITED STATES PATENTS 2,459,844 Seath Jan. 25, 1948 2,556,846 Longacre June 12, 1951 2,589,134 Pyle Mar. 11, 1952 2,720,626 Wing Oct. 11, 1955 FOREIGN PATENTS 239.524 Great Britain Mar. 25, 1926 

